A biosensor refers to a system which transforms the information of a target substance to a recognizable, useful signal. It is a device which consists of a bioreceptor and a signal transducer and selectively detects the substance to be analyzed by transforming the information of the target substance to a recognizable signal. It is very important not only in medical applications for diagnostic purposes but also in basic medical studies of the mechanisms of various biological responses.
Since high selectivity and sensitivity for a specific target substance are required for the biosensor, an effective mechanism should be ensured between the bioreceptor and the signal transducer. For instance, although a biosensor using an enzyme and an antibody has excellent substrate specificity and binding affinity, it is unsatisfactory in terms of stability and cost.
Recently, development of a high-sensitivity fluorescence biosensor using a supramolecular compound and a fluorescent material, which allows for detection of selective binding to a target substance based on change in fluorescence, is drawing a lot of attentions.
In this regard, a variety of fluorescence sensors for detecting cationic, anionic and neutral organic molecules have been developed. These are interesting techniques providing high detection limit and simple operation by detecting fluorescence signals based on changes induced by anionic compounds. In particular, a fluorescence sensor exhibiting selectivity for pyrophosphate (PPi), which plays an important role in signaling and energy storage in biological systems, is advantageous in that it emits fluorescence by the chelate enhanced fluorescence (CHEF) effect upon reaction with a specific anionic compound in the presence of copper ion (patent documents 1 and 2). However, these methods require numerous trials and errors and are time-consuming.
To solve these problems, development of a biosensor which can detect a specific target substance faster and more effectively with high sensitivity is urgently needed.